In 2009, Pope Benedict has told us plainly what happens every time a traditional society makes a purely practical agreement, with modernist Rome:

I myself saw, in the years after 1988, how the return of communities which had been separated from Rome changed their interior attitudes; I saw how returning to the bigger and broader Church enabled them to move beyond one-sided positions and broke down rigidity so that positive energies could emerge for the whole.

Quoted from: http://www.vatican.va/holy_father/benedict_xvi/letters/2009/documents/hf_ben-xvi_let_20090310_remissione-scomunica_en.html

The pope’s observation was right! Look what happened to these groups who made a practical deal with modernist Rome:

We Know Rome’s Plan for the SSPX, when Rome “recognizes” the SSPX (with or without a signed agreement). As Pope Benedict XVI said in 2009, weakening is inevitable for the groups it recognizes. Rome is patient. She waited 11 years for the Society of St. Peter before requiring the clear, dramatic compromises. She waited 5 years for the Institute of Christ the King. She waited as long as needed for the inevitable weakening of each traditional society which she “recognized”.  

As the Vatican’s main negotiator with the SSPX said in the context of one particular conciliar error: “[T]he Traditionalists will not be able to accept [the conciliar teachings on the Jews] immediately. Convincing them will take time, and in this respect we will have to be patient.”  Source: http://vaticaninsider.lastampa.it/en/homepage/the-vatican/detail/articolo/society-of-st-pius-x-di-noia-16482/